This invention is related to a semiconductor article and a method for processing of semiconductor devices. In particular, the invention is directed to an improved method for cleaning unwanted sputter deposits from source/drain surfaces. Further, the invention is particularly directed to performing an in situ cleaning process to remove re-sputtered SiOx deposited on the source/drain surface in a semiconductor device.
During manufacture of a semiconductor device, it is necessary to clean selected surfaces of the device before sputter deposition of a metal, such as cobalt which is intended to form a cobalt silicide as part of the final device structure. During such a prior art process, as shown in FIG. 1, the argon ions 10 tend to sputter SiOx species 12 from the SiO2 spacer material 14 which deposits on other surfaces, such as source/drain surfaces 16. As a result, the contaminating SiOx species 12 on the source/drain surfaces 16 prevent deposition of cobalt onto silicon to form the desired cobalt silicide layer. The resulting CoSi layer is therefore spotty and potentially discontinuous which can result in degraded performance of a semiconductor device 18. It is therefore important to develop a process to prevent re-sputtered SiO2 from depositing on the source/drain surfaces 16.
According to one form of the invention, a semiconductor device is prepared for deposition of a cobalt silicide onto a source/drain region. The device undergoes a first standard sputter pre-clean using an inert gas ion, such as argon. After this sputter pre-clean step, the device surfaces are further cleaned by use of a mixture of silicon hydride, or silanes, and hydrogen (H2). In the most preferred form, H2 is used with SiH4 to assure no deposition of Si. These silicon hydrides can be activated by RF plasma or by an elevated wafer temperature to form SiH2 and SiH3 species. These silane derivatives are applied in situ to the semiconductor device, particularly to source/drain surfaces which are to be cleaned in preparation for formation of a cobalt silicide layer. The silane derivatives act to convert to elemental Si the contaminating SiOx deposits formed from the argon pre-sputter of the SiO2 spacer material present in the semiconductor device.
These and other objects, features and advantages of the invention will be apparent from the following description of the preferred embodiments and examples, taken in conjunction with the accompanying drawings described below.